Field of the Invention
The present invention relates to a light emitting apparatus, an image pickup apparatus and a control method therefor, and more particularly, to control of the light emitting apparatus.
Description of the Related Art
Generally, there is a case where image pickup is performed by an image pickup apparatus such as a digital camera using a light emitting apparatus (also referred to as a flash unit) such as a stroboscopic device (hereinafter, simply referred to as a strobe). In such a case, color balance in image data obtained as a result of image pickup is corrected using luminescent color information (hereinafter, simply referred to as color information) indicating luminescent color of strobe light (see Japanese Laid-Open Patent Publication (Kokai) No. 2008-11557).
While, conventionally, a Xe tube is typically used as a light source of a strobe, in recent years, an LED is more likely to be used as a light source of a strobe in accordance with development of the LED. However, while, in the case of the Xe tube, there is no substantial change in luminescent color during luminescence, in the LED, a temperature of the device increases due to heating caused by luminescence of the LED itself, which may change color information indicating the luminescent color of the strobe light.
FIG. 8 is a diagram for explaining change of color information in the conventional strobe using an LED.
FIG. 8 shows time in a horizontal axis and a device temperature of an LED in a vertical axis. It is assumed here that luminescence of a strobe starts upon start of exposure when image pickup is performed, and the luminescence of the strobe is stopped upon end of the exposure. At this time, the device temperature of the LED changes as indicated by a curve 201 from start of the exposure until the end of the exposure, and the device temperature becomes the highest at the end of the exposure. A region indicated by diagonal lines in FIG. 8 is a region where the device temperature is lower than the device temperature at the end of the exposure.
As shown in FIG. 8, if the device temperature of the LED changes, when it is tried to detect the device temperature after the luminescence is finished to obtain color information, the color information does not include color information at the start of luminescence and during the luminescence, and, thus, there may be an error in the color information.
As a result of correcting color balance of image data according to the color information at the end of luminescence which does not include change of the color information during the luminescence, it is impossible to correct the color balance of the image data with high accuracy.
Further, in the camera disclosed in the above-described Japanese Laid-Open Patent Publication (Kokai) No. 2008-11557, because color information of a light emitting section is obtained by acquiring light reflected at an object using a color sensor, the color information is susceptible to the influence of the object, and, thus, it is also difficult to correct the color balance of the image data with high accuracy.